Electrochemistry of poly(3,4-ethylenedioxythiophene)-polyaniline/Prussian blue electrochromic devices containing an ionic liquid based gel electrolyte film

Electrochromic devices based on poly(3,4-ethylenedioxythiophene) (PEDOT) as the cathodic coloring electrode and polyaniline (PANI) or Prussian blue (PB) as the counter electrode containing a highly conductive, self-supporting, distensible and transparent polymer–gel electrolyte film encapsulating an ionic liquid, 1-butyl-1-methylpyrrolidiniumbis(trifluoromethylsulfonyl)imide, have been fabricated. Polarization, charge transfer and diffusion processes control the electrochemistry of the functional electrodes during coloration and bleaching and these phenomena differ when PEDOT and PANI/PB were employed alternately as working electrodes. While the electrochemical impedance response shows good similitude for PEDOT and PANI electrodes, the responses of PEDOT and PB were significantly different in the PEDOT–PB device, especially during reduction of PB, wherein the overall amplitude of the impedance response is enormous. Large values of the coloration efficiency maxima of 281 cm2 C−1 (λ = 583 nm) and 274 cm2 C−1 (λ = 602 nm), achieved at −1.0 and −1.5 V for the PEDOT–PANI and PEDOT–PB devices have been correlated to the particularly low magnitude of charge transfer resistance and high polarization capacitance operative at the PEDOT–ionic liquid based electrolyte interface at these dc potentials, thus allowing facile ion-transport and consequently resulting in enhanced absorption modulation. Moderately fast switching kinetics and the ability of these devices to sustain about 2500 cycles of clear-to-dark and dark-to-clear without incurring major losses in the optical contrast, along with the ease of construction of these cells in terms of high scalability and reproducibility of the synthetic procedure for fabrication of the electrochromic films and the ionic liquid based gel electrolyte film, are indicators of the promise these devices hold for practical applications like electrochromic windows and displays

Coupled Phenomenological and Fracture Mechanics Approach to Assess the Fracture Behaviour of TWC Piping Component

An attempt has been made in the present work to combine gel and composite polymer electrolyte routes together to form a composite polymeric gel electrolyte that is expected to possess high ionic conductivity with good mechanical integrity. Polyethylene glycol (PEG) based composite gel electrolytes using polyvinyl alcohol (PVA) as guest polymer have been synthesized with 1 molar solution of ammonium thiocyanate (NH4SCN) in dimethyl sulphoxide (DMSO) and electrically characterized. The ionic conductivity measurements indicate that PEG:PVA:NH4SCN-based composite gel electrolytes are superior (σ max = 5.7 × 10−2 S cm−1) to pristine electrolytes (PEG:NH4SCN system) and conductivity variation with filler concentration remains within an order of magnitude. The observed conductivity maxima have been correlated to PEG:PVA:NH4SCN-and PVA:NH4SCN-type complexes. Temperature dependence of conductivity profiles exhibits Arrhenius behaviour in low temperature regime followed by VTF character at higher temperature

Electrochromic performance of a poly(3,4-ethylenedioxythiophene)-Prussian blue device encompassing a free standing proton electrolyte film

Electrochromic devices incorporating an electropolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) film and a free standing, transparent film of a proton conducting polymer electrolyte with high ambient temperature ionic conductivity of 10−2 S cm−1 have been fabricated with and without the ion storage electrodeposited Prussian blue (PB) counter electrode layer. While coloration efficiency increases as a function of applied potential in the sole PEDOT device with largest values of CE(max,VIS) ∼ 120 cm2 C−1 and CE(max,NIR) ∼ 133 cm2 C−1 attained at Vc = −1.9 V, the PEDOT:PB device shows a digression from this trend. Much higher coloration efficiencies in the visible (247 cm2 C−1 at 570 nm) and NIR (116 cm2 C−1 at 1100 nm) regions are achieved for the PEDOT:PB device at a relatively lower reducing voltage of −0.8 V. The PEDOT:PB device shows fast switching redox process (tc = 2.6 s and tb = 1.3 s for a 50% optical contrast at 632.8 nm) and a highly reversible charge density as the ratio of Qinserted to Qextracted was found to vary between 0.8 and 1.0. When switched between the clear and blue states for 2000 cycles, the insignificant drop in peak current density maxima observed for the PEDOT:PB device, i.e. the good cycling stability, the facile fabrication of device assembly, the ease of scaling up the electrolyte and electrochromic coatings, indicate that this method can be adapted as a simple and inexpensive alternative to conventional electrochromic windows with high cost components

Development and modification of PVA-alginate as a suitable immobilization matrix

This study reports the immobilization of invertase in the PVA-alginate matrix via a modified method. The PVA-alginate modified method involved the treatment of immobilized beads in sodium sulfate solution. In this study, the steps involved in the preparation of matrix were analyzed. The influence of the sodium sulfate concentration on the bead formation was investigated and its mechanism of immobilization was further elucidated by means of FTIR and EDX. In addition, the stability of invertase in sodium sulfate and boric acid solution was also studied. EDX results revealed that borates were completely replaced by sulfates as the cross-linking agent. Through the mechanism of nucleophilic substitution, it was revealed that sulfate attacked the carbon atom bearing borate on the opposite side to the side bonded to borate due to steric hindrance. Carbon therefore underwent backside attack by sulfate and inverted its original configuration through a phenomenon known as Walden Inversion. The presence of sulfate was also supported by FTIR spectra. The best sodium sulfate concentration was found to be 0.5 M

Role of polyvinyl alcohol in the conductivity behaviour of polyethylene glycol-based composite gel electrolytes.

An attempt has been made in the present work to combine gel and composite polymer electrolyte routes together to form a composite polymeric gel electrolyte that is expected to possess high ionic conductivity with good mechanical integrity. Polyethylene\ glycol (PEG) based composite gel electrolytes using polyvinyl alcohol (PVA) as guest polymer have been synthesized with 1 molar solution of ammonium thiocyanate (NH4SCN) in dimethyl sulphoxide (DMSO) and electrically characterized. The ionic conductivity measurements indicate that PEG:PVA:NH4SCN-based composite gel electrolytes are superior (σmax = 5.7×10 −2 S cm −1) to pristine electrolytes (PEG :NH4SCN system) and conductivity variation with filler concentration remains within an order of magnitude. The observed conductivity maxima have been correlated to PEG:PVA:NH4SCN- and PVA:NH4SCN-type complexes. Temperature dependence of conductivity profiles exhibits Arrhenius behaviour in low temperature regime followed by VTF character at higher temperature. Keywords. Polymer blend; gel